It is a common practice in the prior art to subject inorganic particles to plasma treatment to render their surfaces more hydrophilic and wettable, so that the particles may be readily dispersed in aqueous solvents or improved in dispersion in organic solvents and resins. JP-A H06-000635 (Patent Document 1) describes an exemplary method of hydrophilizing surfaces of alumina particles via atmospheric plasma treatment. JP-A H06-134296 (Patent Document 2) describes an exemplary method of hydrophilizing surfaces of titania or alumina particles via atmospheric plasma treatment. JP-A H06-285365 (Patent Document 3) describes an exemplary method of hydrophilizing surfaces of titania particles via atmospheric plasma treatment. JP-A 2010-275334 (Patent Document 4) discloses plasma treatment of silica particles to improve their dispersion in epoxy resins.
Meanwhile, silicone particles are used from the past in cosmetics for the purposes of imparting silky, smooth and pleasant feels on use, ease of spreading, and soft focus effect. The silicone, however, has the problem that it is so water repellent that it may be dispersed in aqueous cosmetic compositions with difficulty. The additional use of surfactants or the surface treatment of particles makes it possible to disperse silicone particles in water. However, since the surfactants are suspicious of skin irritation, it is sometimes avoided to use surfactants in those cosmetics applied externally to the skin such as skin care cosmetics, make-up cosmetics, antiperspirant cosmetics, and UV care cosmetics.